Fatigue Performance Analysis Of Concrete Beams Strengthened With External Prestressing After Corrosion

In recent years,steel corrosion has become a major factor to affect the performance of the bridge structure.Under the repeated action of vehicle load,the stiffness and the fatigue life of the beams are gradually reduced with the corrosion of the steel bar.Therefore,the corroded beam is strengthened by the external prestressing steel strand after galvanized anti-corrosion treatment,which can improve the mechanical properties of the steel.In order to further understand the influence of bridge structure on the fatigue behavior of beams strengthened by external prestressing strand under different corrosion degree.In order to further understand the bridge structure under different corrosion degree,the influence of external prestressing strand reinforcement on the fatigue behavior of the structure.In this paper,the fatigue behavior of strengthened test beams with different corrosion rates are compared,in order to obtain the effect of external prestressing steel strand on the corroded beam.The main research contents and conclusions are as follows:1.The basic composition of external prestressing reinforcement system is understood,analyzing the mechanical properties of external prestressed structure,and the calculation method of the ultimate bearing capacity is determined,laying the theoretical foundation for further experimental design.2.The corrosion test of the test beam was carried out by electrochemical acceleration method and internal mixing salt method.The external steel strands are symmetrically arranged on both sides of the beam,the steering blocks are arranged in three-point.The corroded beam is strengthened by external prestressing strand which uses the form of one side symmetrical grading tension.3.Static test on beams with six different corrosion rate and reinforcement was carried out,determining the cracking load and the ultimate load of the beams,and analyzing the failure modes,cross section strain,the strain of the steel bar and external steel strand,deflection and other factors under static load.The results show that the external prestressed reinforcement method can effectively prevent brittle failure of the corroded beams.With the increase of corrosion degree,the bearing capacity and flexural stiffness of the member are increased by the external prestressing reinforcement.4.Fatigue test on beams with six different corrosion rate and reinforcement was also carried out,analyzing the failure mode,fatigue life,concrete compressive strain,the strain of the steel bar and external steel strand,the variation law of the mid-span deflection and stiffness under the action of fatigue load.The results show that the external prestressed steel strand reinforcement can improve the anti corrosion fatigue properties of test beams,and the fatigue life of corroded beams are obviously improved.Bending stiffness increases gradually with the increase of the corrosion rate.5.Through the introduction of the stiffness correction coefficient of corrosion and fatigue action,the calculation formula of the deflection of corroded concrete beams by external prestressing reinforcement is presented.Compared the calculated results with the measured results,which proves the reliability of the formula.